LIARD BASIN – MIDDLE EXPLORATION

Warren Walsh1, Osman Salad Hersi2, Mark Hayes1

ABSTRACT The Liard Basin is a sub-basin of the Western Sedimentary Basin (WCSB) system, straddling the Northwest and Yukon Territories boundary with the Province of . The basin contains over 5 km of sedimentary strata of through Upper age. Exploration for Manetoe Dolomite reservoirs hosted within middle Devonian carbonates of the Dunedin and Nahanni formations began in the 1950’s. Several pools have been found within the fold and thrust belt both in Northeastern British Columbia and the Yukon and Northwest Territories. Recent gas discoveries within the Devonian Nahanni Formation north of Fort Liard, NWT has renewed interest in this play. Resource assessments for the middle Devonian play in the Liard Basin estimates between 2.8 and 6.6 Tcf undiscovered gas, with approximately 2.5 Tcf estimated to be located within Northeastern British Columbia. The British Columbia Ministry of Energy and Mines (BC MEM) is currently working with the University of Regina and the Geological Survey of Canada (GSC) to expand our knowledge and understanding of the Liard Basin. Through a contribution agreement, the BC MEM, in conjunction with Dr. Osman Salad Hersi of the University of Regina, is supporting graduate level studies on the sedimentology, stratigraphy and diagenesis of Middle Devonian, shallow-marine carbonates of the Dunedin Formation of subsurface Liard Basin, with application to petroleum exploration. The BC MEM also continues their relationship with the GSC, who has recently published a reinterpretation of the Bovie Structure which included the identification of new conceptual plays within the Liard Basin.

Warren Walsh, Osman Salad Hersi, Mark Hayes, Liard Basin – Middle Devonian Exploration in Summary of Activities 2005, BC Ministry of Energy and Mines, pages 38-41. 1Resource Development and Geoscience Branch, BC Ministry of Energy and Mines, PO Box 9323, Victoria BC, V8W 9N3 2Department of Geology, University of Regina, Regina, SK, S4S 0A2 Keywords: Northeastern British Columbia, Liard Basin, Dunedin Formation, Manetoe Dolomite Facie Devonian, and Cretaceous strata associated with the Bovie Fault (MacLean and Morrow, 2004). INTRODUCTION The western side of the Liard Basin is referred to as the Liard Plateau or the Liard Fold and Thrust Belt, a The Liard Basin is a sub-basin of the extensive northward continuation of the fold and thrust belt of the Western Canada Sedimentary Basin (WCSB) system, Rocky Mountain foothills. Within this area, several straddling the Northwest and Yukon Territories boundary hydrocarbon pools have been discovered within with the Province of British Columbia. The basin covers a carbonates of the middle Devonian and several gas shows total area of approximately 2.5 million hectares with up to have been found at Mississippian through 5000 m of Paleozoic and Mesozoic sedimentary fill. The intervals. The middle Devonian carbonate play type has Liard Basin is a frontier basin whose hydrocarbon upwards of 2.35 Tcf of remaining undiscovered gas in potential is only just beginning to be appreciated. place within Northeastern British Columbia (NEB, 2000). The eastern boundary of the Liard basin is delineated The stratigraphy, sedimentology and diagenetic history of by the Bovie Fault System, which also marks the the middle Devonian Dunedin Formation of British approximate eastern limit of Mississippian through Upper Columbia is the focus of a multi-year collaboration Cretaceous strata (Monahan, 2000). Recent work by the between the University of Regina and the BC MEM. Geological Survey of Canada (GSC), supported by the A geological map of the Liard Basin has been created British Columbia Ministry of Energy and Mines (BC and is now available to aid exploration. The 1:250 000 MEM) has reinterpreted the nature and history of the scale map is a compilation of geology maps separately Bovie Structure (MacLean, 2002; MacLean and Morrow, issued by the Geological Survey of Canada and has been 2004). MacLean and Morrow (2004) have reinterpreted updated with infrastructure, land tenure and petroleum the Bovie Fault as a two-stage compression; (i) a late- and natural gas wells for the entire Liard Basin. Carboniferous to Permian westward convergent steeply Production data and Drill Stem Test results and dipping thrust fault, which is cut by (ii) the Larimide aged interpretation for the middle Devonian have also been Bovie Lake Thrust. This reinterpretation of the Bovie summarized. Structure has also identified several potential play types in

Summary of Activities 2005 38. GEOLOGIC SETTING, Lake, 1989, Morrow and Davies, 2001). The dolomitized strata are known as the Manetoe Dolomite Facies PALEOGEOGRAPHY, AND (Manetoe) in the Northwest and Yukon territories STRATIGRAPHY (Morrow and Potter, 1998; Morrow et al. 1986, 1990); they form good reservoir intervals in many gas-producing fields in the region (e.g., Pointed Mountain, Kotaneelee, Dunedin Formation Fort Liard, Beaver River and Crow River gas fields). The Manetoe is characterized by a fractured and brecciated In the Devonian Period, NE BC and nearby regions white sparry dolomite (Morrow et al. 1990; Morrow and of Alberta, Yukon and Northwest Territories were cut by Potter, 1998). Although the Manetoe dolomite facies that several rifting events that produced deep depressions and occur within the Dunedin and Nahanni-Landry uplifted shoulders that later became shallow marine shelf successions of Yukon and NWT, respectively are fairly areas (Cecile et al. 1997, Pyle et al. 2003). The well documented (Morrow and Potter, 1998; Morrow and Macdonald-Mackenzie shelf was the most prominent in Davies, 2001, Morrow et al. 1986, 1990), knowledge is northeastern British Columbia and nearby regions, lacking in NE BC, as the equivalent dolomites of the allowing deposition of thick carbonate successions that Dunedin Formation are relatively less understood. include the largest carbonate reservoirs in the region Understanding the origin, fabric, porosity, reservoir (Moore, 1989, Pyle et al. 2003). potential and vertical and lateral distributions of this The Dunedin Formation consists of Middle Devonian dolomite facies is essential for gas exploration activities (Eifelian) carbonate strata that were deposited on the within this prospective frontier basin. MacDonald Shelf. The shelf continued across the B.C.’s border with the Yukon and Northwest territories where equivalent strata, the Landry-Nahanni formations, were MIDDLE DEVONIAN HYDROCARBON deposited. Southward (i.e., Southern NE BC and NW Alberta), the Dunedin Formation merges with the prolific POTENTIAL (Nadjiwon, 2001). These middle Devonian carbonates contain hydrothermally dolomitized facies (Manetoe dolomite facies and equivalents; see Fold and Thrust Belt below) with potentially good reservoir quality. Exploration to date for middle Devonian Manetoe The Dunedin Formation is a transgressive unit Dolomite within the Dunedin and Nahanni formations has dominated by peritidal and subtidal shallow marine been focused within the Liard Fold and Thrust Belt. The carbonates and, due to southward facies retrogradation, Liard fold and thrust belt of BC covers an area of the oversteps the Dunedin approximately 1.25 million hectares. Exploration has Formation in the southeastern (Morrow, 1978, Nadjiwon, resulted in the discovery of two fields, Beaver River and 2001). Broad subdivision of the Dunedin Formation Crow River. Outside of these two fields, only 6 documents that the formation consists of a lower exploration wells have been drilled targeting the middle lithofacies characterized by a bioclastic dolomitic Devonian, all drilled prior to 1974. Within the Yukon and wackestone and an upper lithofacies of a bioclastic NWT, a total of 5 middle Devonian fields have been grainstone to wackestone units (Morrow, 1978, Nadjiwon, discovered with less than 10 exploration wells outside of 2001). Further south, where the formation passes to the proven fields. reefal Keg River Formation, intercalations of and Exploration within the Liard basin began in the stromatoporoid reef facies are common. Due to the reefal 1950’s with the first well drilled in the Liard Fold belt at “tongues”, the thickness of the Dunedin Formation varies the Toad River Anticline (Joint Venture No. 1 c-10-E/94- significantly (e.g., from 108 m to over 300 m within a N-7; rig released in 1954). Amoco Canada Petroleum Co. distance of 11 km, Nadjiwon et al., 2000), however, Ltd. made the first discovery at the Beaver River Field in causes of this abrupt thickness change are not clear. 1958. Further drilling delineating the Beaver River pool Possibilities may include synsedimentary faulting and/or and subsequent discoveries were made in the 1960’s at establishment of reefal margin defined by differential reef Pointed Mountain in the North West Territories and growth responses to sea level fluctuations (cf. Kotaneelee, Yukon Territory. Originally over 1.4 Tcf of transgression-instigated catch-up situation of Jones and reserves were associated with the Beaver River pool Desrochers, 1992). The Dunedin Formation continues alone, however, high water to gas ratios resulting from the across the northern provincial-territorial borders where it highly fractured reservoir and active water drive led to is equivalent with the gas-producing Landry-Nahanni lower than expected recoveries from these fields, which Formation in the Yukon and Northwest territories. were subsequently shut-in during the mid-1970’s (see Davidson and Snowdon, 1978). Recent exploration has resulted in new pools being discovered in the Fort Liard The Manetoe Dolomite Facies region, NWT. Beyond this however, there has been only Dolomites associated with subsurface middle limited exploration for Devonian aged reservoirs within Devonian carbonates of southeast Yukon Territory, the Liard Basin. southwest Northwest Territories and NE BC host one of In the past, resource assessments have been the world’s largest Mississippi Valley-type (MVT) conducted with the aim to identify the resource potential deposits (Rhodes et al. 1984, Qing, 1998). These of the Liard Basin. The National Energy Board (NEB) dolomites are also important gas reservoirs (Collins and assessed the resource potential for the NE BC portion of

39 British Columbia Ministry of Energy and Mines the play to be 2.5 Tcf of ultimate resource total, with 2.35 facies). These goals are achievable by performing and Tcf remaining undiscovered. A 2001 assessment of the integrating detailed sedimentological, lithostratigraphic, Manetoe Facies reservoirs in the Yukon assigned an IGIP biostratigrpahic analyses, 3-D lithofacies mapping of the of 3.4 Tcf. This is a total ultimate resource potential of 5.9 formation (integrating subsurface data with interpretation Tcf, though it does not include the NWT. For the entire of seismic profiles) and detailed diagenetic studies, fold and thrust belt, the natural gas potential in Canada porosity evolution and reservoir characterization of the was assessed in 2001 by the Canadian Gas Potential formation. Integration of these data interpreted in the light Committee (CGPC) as a total IGIP of 5.6 Tcf (CGPC, of sequence stratigraphic approach will also better 2001), with 2.8 Tcf remaining undiscovered, mainly in constrain the 3-D evolution of the depositional systems middle Devonian reservoirs. through time and space. This will eventually enhance our understanding of the lateral and vertical distributions of the reservoirs. The overall scope of the proposed research Basin Center / Bovie Fault Zone is the enhancement of our knowledge with respect to the nature and internal architecture of this formation, The center of the basin between the western foothills diagenesis and subsurface distribution of the dolomite and the Bovie Fault zone covers approximately 1.0 facies associated with the formation and reservoir million hectares. Within this immense area only two characterization of both dolomitized and undolomitized wells, Amoco et al. La Biche (a-67-D/94-O-13 RR: 1974- intervals of the formation. 08-28) and Burlington Chevron Patry (c-86-B/94-O-5/02 RR: 2000-01-25), have penetrated middle Devonian The Ministry of Energy and Mines continues their carbonates. Subsea depth to the middle Devonian relationship with the Geological Survey of Canada (GSC) carbonate in these wells is -4635m (15,207’) and -3696m through support for their ongoing work on the Liard (12,126’) respectively. Burlington Chevron Patry found Basin. The Geological Survey of Canada is continuing dolomite at a depth of -3846 m (subsea). However, of interdisciplinary studies incorporating seismic, these wells, only Amoco et al. La Biche was tested. Two stratigraphy and source rock studies (see Morrow et al. drill stem tests were run over the middle Devonian 2002; Morrow and Shinduke, 2003; Potter et al., 2003; carbonate, with an inhibited water cushion of 2590m. No Maclean and Morrow, 2004). blow was recorded during the flow and recoveries were not recorded, as the tool became stuck in the hole following the second test, however, a sample bomb did REFERENCES recover gas (97% C1) from the second DST. These wells indicate that both dolomite and gas are present within the Canadian Gas Potential Committee (CGPC), 2001. Natural Gas middle Devonian carbonates of the Liard Basin center. Potential in Canada, 2001, Published by the CGPC, Calgary. To date, no resource assessment has been made for Cecile, M.P., D.W. Morrow, and G.K. Williams. 1997. Early the middle Devonian within the Liard Basin center. Paleozoic (Cambrian to Early Devonian)tectonic However, conceptual plays along the western margin of framework, Canadian Cordillera. Bulletin of Canadian the Bovie Structure were identified by MacLean and Petroleum Geology, v. 45, p. 54-74. Morrow, 2004. Collins, J.F. and Lake, J.H. 1989. Sierra reef complex, Middle Devonian, northeastern British Columbia. In: Reefs, Canada and adjacent areas. H.H.J. Geldsetzer, N.P. James and G.E. Tebutt (eds.). Calgary, Canadian Society of FUTURE WORK Petroleum Geologists, Memoir 13, p. 414-421. Davidson, D.A. and Snowdon, D.M. 1978. Beaver River Middle The sedimentologic, stratigraphic and diagenetic Devonian carbonate: Performance review of a high-relief attributes of the Dunedin Formation and its basin-fill gas reservoir with water influx; Journal of Petroleum architecture of the Middle Devonian Dunedin Formation Technology, p. 1673-1678. (NE BC) are not well understood despite the high Government of Yukon, Oil and Gas Resources Branch. 2001. Petroleum Resources Assessment of the Liard Plateau, potential of hydrocarbon content. In order to attract Yukon Territory, Canada. National Energy Board for industry interest to this frontier basin, a clear Energy Resources Branch, Whitehorse, Yukon, Open File: understanding of these attributes and reservoir qualities of ISBN 1-55018-801-1. the Dunedin Formation is crucial. The Ministry of Energy Jones, B. and Desrochers, A. 1992. Shallow platform and Mines is working with Dr. Osman Hersi of the carbonates. In: Facies Models – Response to sea level University of Regina through a contribution agreement change. Edited by Walker, R.G, and James, N.P. supporting graduate level studies on the sedimentology, Geological Association of Canada, 277-301. stratigraphy and diagenesis of Middle Devonian Dunedin Moore, P.F. 1989. Devonian reefs in Canada and some adjacent Formation shallow water carbonates of subsurface Liard areas. In: Reefs, Canada and adjacent area. Edited by Geldsetzer, H.H.J. and James, N.P, and Tebbutt, G.E. Basin, with application to petroleum exploration. 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Summary of Activities 2005 40. Monahan, P., 2000. Stratigraphy and potential hydrocarbon objectives of Mississippian to lower Cretaceous strata in the eastern Liard Basin area. CD-ROM. Government of British Columbia. Crown Publications Inc. Inventory #667 Morrow, D.W. and Davies, G.R. 2001. The Liard Basin Manetoe Dolomite: A new look at a frontier deep gas play. CSPG Convention, abstracts: C-028, p. 28-1 – 28-5. Morrow, D.W. and MacLean, B.C. 2004. Bovie Structure: its evolution and regional context; Bulletin of Canadian Petroleum Geology V. 52, p. 302-324. Morrow, D. W. and Shinduke, R. 2003. Liard Basin, Northeast British Columbia: An exploration frontier. CSEG Convention, Calgary, 2003, Abstract#283S0131: Morrow, D.W., Cumming, G.L., and Koepnick, R.B. 1986. Manetoe Facies – a gas-bearing megacrystalline, Devonian dolomite, Yukon and Northwest territories, Canada. AAPG, 70:702-720 Morrow, D.W., Aulstead, K.L., and Cumming, G.L. 1990. The gas-bearing Devonian Manetoe Facies, Yukon and NW territories. Geol. Surv. Can. Bull. 400:1-54. Morrow, D. W. MacLean, B.C., and Lane, L.S. 2002. Liard Basin: tectonic evolution and petroleum potential. CSEG Convention – extended abstract, June 3-7, 2002, Calgary http://www.cseg.ca/conferences/2003/2003abstracts/283S0 131.pdf Nadjiwon, L.M. 2001. Facies analysis, diagenesis and correlation of the middle Devonian Dunedin and Keg River Formations, Northeastern British Columbia. M.S. thesis, Univ. of Waterloo, Waterloo, Ontario. Nadjiwon, L.M., Morrow, D.W. and Coniglio, M. 2000. Middle Devonian Dunedin and Keg River formations: Sedimentation style and facies changes along an inner continental shelf. CSEG Conference, Calgary, abstract#426 National Energy Board, 2000. Northeast British Columbia Natural Gas Resource Assessment 1992-1997. Technical Report. Potter, J., Goodarzi, F., Morrow, D.W., Richards, B.C., and Snowdon, L.R. 2003. Organic petrology, thermal maturity and Rock-Eval/TOC data for upper Paleozoic to Upper Cretaceous strata from wells near , northeast British Columbia. Geological Survey of Canada Open File 1751 Pyle, L.J., Orchard, M.J., Barnes, C.R. and Landry, M.L. 2003. Conodont biostratigraphy of the Lower to MiddleDevonian Deserters Formation (new), Road River Group, northeastern British Columbia. Canadian Journal of Earth Sciences, 40:99-113. Qing, H. 1998. Petrography and geochemistry of early-stage, fine- and medium-crystalline dolomites in the Middle Devonian Presqu’ile Barrier at Pine Point, Canada. Sedimentology, 45:433-4446. Rhodes, D., Lantos, E.A., Lantos, J.A, Webb, R.J. and Owens, D.C. 1984. Pine Point orebodies and their relationship to the stratigraphy, structure, dolomitization, and karstification of the Middle Devonian barrier complex. Economic Geology, 79:991-1055.

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